Apparatus for producing cement sheets

ABSTRACT

Apparatus for producing a cement sheet, including a rotatable mould into which a cement mix is fed to form a soft, centrifugally moulded cylinder, which is then removed from the mould, divided longitudinally, and laid out flat to harden. The mould is initially fitted with a flexible liner of metal, rubber or plastics. The soft cement cylinder is removed by means of a mandrel inserted into the cylinder while in the mould. During removal from the mould, the cement cylinder is held onto the mandrel either by vacuum applied to perforations in the wall of the mandrel, or by connecting together the edges of the liner which surrounds the cylinder while it is removed from the mould on the mandrel. The longitudinal division in the cement cylinder may be formed by a longitudinal inwardly projecting member within the mould or forming part of the liner, or by slitting the cylinder on the mandrel after its removal from the mould. The apparatus is particularly useful for producing small quantities of asbestos cement sheets with special laminations or surface effects. Apparatus in accordance with the invention may be used for producing sheets of flowable hardenable material other than cement.

Barratt Dec. 11, 1973 APPARATUS FOR PRODUCING CEMENT SHEETS [76]Inventor: William C. Barratt, 595 Sheppard St., Niagara Falls, Ontario,Canada [22] Filed: Jan. 3, 1973 [21] Appl. No.: 320,768

Related US. Application Data [63] Continuation-in part of Ser. No.166,780, July 28,

1971, abandoned.

[30] 7 Foreign Application Priority Data Feb. 1, 1972 Great Britain..4712/72 [52] US. Cl 425/86, 264/311, 425/297, 425/435, 425/436 [51]Int. Cl B281) 21/08 [58] Field of Search 425/86, 182, 297,

425/308, 324, 425, 426, 427, 435, 436, DIG. 44, DIG. 124; 249/112;264/86, 159, 311

Primary Examiner-H. A. Kilby, Jr. Attorney-John W. Malley et al.

[57] ABSTRACT Apparatus for producing a cement sheet, including arotatable mould into which a cement mix is fed to form a soft,centrifugally moulded cylinder, which is then removed from the mould,divided longitudinally, and laid out flat to harden. The mould isinitially fitted with a flexible liner of metal, rubber or plastics. Thesoft cement cylinder is removed by means of a mandrel inserted into thecylinder while in the mould. During removal from the mould, the cementcylinder is held onto the mandrel either by vacuum applied toperforations in the wall of the mandrel, or by connecting together theedges of the liner which surrounds the cylinder while it is removed fromthe mould on the mandrel. The longitudinal division in the cementcylinder may be formed by a longitudinal inwardly projecting memberwithin the mould or forming part of the liner, or by slitting thecylinder on the mandrel after its removal from the mould. The apparatusis particularly useful for producing small quantities of asbestos cementsheets with special laminations or surface effects. Apparatus inaccordance with the invention may be used for producing sheets offlowable hardenable material other than cement.

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SHEET 1M)! 14 APPARATUS FOR PRODUCING CEMENT SHEETS This application isa continuation-in-part of my United States Patent Application Ser. No.166,780, filed July 28, 1971 now abandoned.

The present invention relates to apparatus for producing sheets from aflowable hardenable material such as cement, which sheets may be flat,curved or contoured. This invention provides apparatus for performingthe process of co-pending Patent Application Ser. No. 166,778 also filedJuly 28, 1971. The sheets may be used either as produced or cut tosmaller sizes, for example as structural members, wall panels, or roofsections, or for decorative components such as tiles, moulds, millworkor shingles.

In the known wet process for manufacturing cement sheets, andparticularly asbestos cement sheets, a large plant is required which inorder to be economical must operate on a high production basis, and sucha process is not easily adapted for producing small quantities ofspecial decorative materials.

The present invention provides apparatus which is suited to theeconomical production of small quantities of cement sheets, and whichcan readily be adapted to produce a wide variety of surface finishes, orother characteristics, in the cement sheets produced. The apparatusproduces the cement sheets singly, one after the other, and it is a verysimple matter to modify the operation of the apparatus betweenindividual sheets, so that a wide variety of different cement sheets canbe produced in a short time. The cement sheets can vary as to thickness,composition, colour, and the nature and shape of the surface finish. Theapparatus thus is very suitable for producing a lot of differentcomponents, having different shapes and surface finishes, for a singlebuilding. The apparatus used in accordance with the invention does notrequire a large investment or take up a large amount of space, so thatit is very suitable for location in the locality where building istaking place. Furthermore, the nature of the process used gives a highstrength product due to avoidance of excess water, uniformity of wallthickness, high density and predetermined directional resistance tostresses. In the case of cement reinforced by fibres, such as asbestoscement, additional strength is given by good orientation and formationof fibres. Also, the process operates with very little waste.

In the process described in copending application Ser. No. 166,778 acement sheet is produced by a centrifugal casting method, the cement mix(including water) being fed into a rotatable cylindrical mould and spunto distribute the mix evenly around the mould wall to shape the mix intoa hollow cement cylinder. One end plate of the mould is removable toallow for axial removal of the cement cylinder, and in order to effectthis removal a cylindrical mandrel is inserted into the mould to engagethe inner surface of the cement cylinder, which is then withdrawn on themandrel. After removal, and with the cement cylinder still in the softor flaccid state, the cement cylinder is divided longitudinally and theresultant sheet is laid out onto a flat or curved surface and allowed toharden. Before hardening, the cement sheet may be pressed between twoplatens, and one of these platens may carry a design in relief toproduce a corresponding relief design on the cement sheet.

The present invention provides apparatus for performing this processcomprising:

a. a cylindrical mould mounted for rotation on a horizontal axis andhaving a removable end plate, said mould and end plate being such that acylindrical body formed within the mould. can be extracted by slidingwithout dimensional change after removal of said end plate;

b. means for feeding said material directly onto the inner surface of aliner held within said mould,

c. a mandrel movable axially into the mould through the end of the mouldhaving the removable end plate, said mandrel having a cylindricalsurface engageable with the inside surface of a hollow cylindrical bodyof the material formed within the mould by spinning,

d. mounting means for said mandrel allowing move ment thereof axiallyinto the mould and also allowing rotation thereof after removal from themould and allowing relative transverse movement between the mandrel anda receiving surface for the sheet,

e. a flexible liner dimensioned to fit within the cylindrical innersurface of the mould, the edges of said liner which are adjacent eachother when in the mould being provided with radially extending elements,

. releasable connecting means for holding said radially extendingelements to prevent separation thereof after removal of said. mandrel,with said hollow cylindrical body and said liner, from the mould, and

g. means for forming a longitudinal division in said cement body, toallow the body to be unrolled from the mandrel after removal from themould.

The mandrel mounting means may be a special railmounted carriage, orordinary handling means such as a crane or hoist.

The means for forming a longitudinal division in the cement cylinder maybe slitting means such as a blade or a wire band saw, applied to theunderside of the cylinder while held on the mandrel. Alternatively, themould or the liner may be provided with an inwardly projecting memberarranged to form a longitudinal discontinuity in the cylinder formed inthe mould, in which case the dividing step involves merely splitting thecylinder along this discontinuity.

The flexible liner may be formed for example of sheet metal or rubber,bendable to form a cylindrical surface within the mould, and having alongitudinal division so that it may be laid out flat with the sheet ofmaterial formed in the mould. The radially extending elements may beflanges on the liner edges, extending outwardly or inwardly, releasablemeans being provided for connecting these together when the mandrel isinside the cylinder so that the liner can assist in holding the cylinderonto the mandrel. The liner edge portions may be directly connectedtogether, as by means of a clip, or may be indirectly connected togetheras by being individually connected to holding means carried by themandrel. The liner may become incorporated in the final product, or maybe separated from the final sheet and re-used. The adjacent edgeportions of the liner may be spaced apart (while surrounding thecylinder) so as to allow the cylinder to be slit through the gap betweenthe edge portions. Alternatively, an edge portion of the liner may bebent inwardly to form an inwardly projecting member within the mould,this member forming a longitudinal discontinuity in the cylinder so thatno slitting step is required.

The process and apparatus will be particularly described by way ofexample with reference to the accompanying drawings in which:

FIG. 1 is a partly sectioned elevation of a first type of centrifugalmould for use in accordance with the invention;

FIG. 2 is a cross section on lines 22 of FIG. 1 showing details of linerlocking means,

FIG. 3 is a partly broken-away side view of a mandrel suitable for usewith the apparatus of FIGS. 1 and 2,

FIG. 4 is a sectional view of the mandrel on lines 4-4 of FIG. 3,

FIG. 5 is a partly sectioned view of the mould of FIG. 1 with themandrel in place,

FIGS. 6a, 6b and 6c illustrate modified apparatus for slitting, layingout and curing the cement sheets,

FIG. 7 is a partly sectioned elevation ofa second type of centrifugalmould with a removable liner in place,

FIG. 8 is an enlarged view in cross-section of a portion of the mould,on lines 8-8 of FIG. 7,

FIG. 9 is a sectional view of a mandrel for use with the mould of FIGS.7 and 8,

FIG. 10 is an enlarged view of a cross-section through the mandrel online 10-10 of FIG. 9,

FIGS. 11 and 12 show diagrammatic end views of the mould of FIGS. 7 and8 with the mandrel of FIG. 9 inserted therein, at different stages inthe process,

FIG. 13 is a view of the mandrel of FIG. 9 in the last stage of theprocess,

FIG. 14 shows an enlarged view of a platen with the cement sheet laidout thereon,

FIG. 15 shows a partly sectioned view of a combined vacuum and linerholding mandrel,

FIG. 16 shows a cross-sectional view of part of the mandrel of FIG. 15engaging a cement cylinder within a mould, and

FIG. 17 shows an end view of a mould with modified means for removingwater from the cement.

Referring to FIGS. 1 and 2, the apparatus includes a rotatablecentrifugal mould having a cylindrical wall 112. The mould wall 112 isreinforced by reinforcing rings or tires 115 which rest on four rollers116. The rollers 116 are carried by two parallel horizontal shafts 117,supported in bearings 118, and one of these shafts is driven by a motorand gearbox combination 119. When the motor is operated to drive theshaft 117, the frictional contact between rollers 116 and the tires 115causes the mould to rotate about its horizontal axis.

The mould has at one end an axially movable annular member 121, and atthe other end a removable end plate 122. The annular member 121 istermed a void ring, and this void ring is of channe form, having anoutwardly facing opening engaged by an annular plate 180 which is boltedto the end flange of the mould. The void ring is movable axially of themould between the positions shown in FIGS. 1 and 5 and sealing means 181provide a seal between the inner flange of the ring and the innersurface of the mould. The void ring 121 has a radial dimension greaterthan that of the thickest cylinders to be spun within the mould, and hasinterior dimensions large anough to allow space for entry of a charginghead 23 which is described hereinafter.

The removable end plate 122 is mounted on an axially projecting stubshaft 126, which is carried in a bearing 127 supported at the end of aswing arm 128. The swing arm is pivoted at 130 and is rotatable from theclosed position of FIG. 1 to the open position of FIG. 3 by means of apower cylinder (not shown). The inside of end plate 122 is provided witha central locating ring 133 having an inner surface which flaresoutwardly towards the other end of the mould, and which serves tosupport and locate one end of the charging head 23.

It will be apparent that the end plate 122 need not entirely cover theend of the mould, but may instead provide a cover over an annularportion only, of radial thickness greater than that of the cylinder tobe spun therein.

The charging head 23, as shown in FIG. 1, is mounted on a supportcarriage 24 mounted on rails 24a adjacent that end of the mould with thefixed end plate. These rails allow movement of the charging head fromthe operative position of FIG. 1, in which the charging head extendsthrough the fixed void ring 121, to a retracted position in which thecharging head is withdrawn clear of the mould.

The charging head comprises a horizontally extending support membersomewhat longer than the mould in the form of a parallel sided channel34 open at its lower end and reinforced at its top by a horizontal plate34b. At its outer end (remote from the carriage 24) the plate 34bcarries a positioning pin 35, which, when the charging head is in theposition of FIG. 1, locates in the locating ring 133 and assists insupporting the outer end of the charging head. The support membercarries at one side a cement feed pipe 36, having downwardly extendingdistribution pipes 36a spaced along the pipe 36 at 1 foot spacing. Belowthe lower ends of pipes 36a there is provided a curved shutter 38 which,when in the closed position shown in broken lines, co-operates with theoutside of the channel 34 to provide a trough suitable for retaining aquantity of particulate material. The shutter 38 is mounted on radialarms 39 pivoted to the support member at and pivotally movable relativeto the support member by fluid cylinder 81 to move ths shutter into theopen position shown in full lines, allowing material held in the shutterto be released onto the inside of the mould or to be fed directly intothe mould from discharge pipes 36a.

The channel 34 accommodates a hollow, parallel sided member 83vertically slidable therein under the control of hydraulic cylinder 84.The lower end of member 83 has a curved cornerjoining the vertical sideof the member 83 with the horizontal lower edge thereof, this curvedcorner facing the direction of rotation of the mould which direction isindicated by the arrow. This curved corner and the adjacent surfaces ofmember 83 form spreader means 86 having a hard facing and capable ofcontacting the inner surface of a hollow cylinder of material being fedinto the mould, to assist in evenly spreading the material within themould. During the stage in which material is being fed into the mouldvia pipes 36a, the spreader means is caused to rise at a steady rateunder control of fluid cylinder 84.

The member 83 also incorporates means for removing water from within thecentre of the cylinder of material being spun within the mould, in theform of a skimmer 88 which is movable by fluid cylinder 89 be tween aretracted position in which it does not extend below the surface of thespreader means, to an extended position as shown in broken lines inwhich it projects. below the lower surface of the spreader means. Theskimmer 88 has an opening facing the direction of rotation of the mould,and which communicates with a water discharge pipe 90 extending alongthe member 83.

The member 83 also incorporates a vibrator 92 mounted on the inside ofthe spreader means and arranged to cause vibration of the spreader meansfor compacting material in the mould.

FIG. 2 also shows a special form of liner 170 used in this embodiment.This liner is a sheet of abrasion resistant rubber of 7% inch (12 mm)thickness sufficiently flexible to form a cylinder lining the mould asshown. The liner has opposite edge portions which are adjacent while theliner is in the mould, the edge portions being bonded to sheet metaledge pieces 171. The edges of the liner extend beyond the edge pieces171 to form a seal preventing cement or other material from passingbetween the edge pieces 171. The edge pieces 171 are provided withradially outwardly directed flanges 172 which are spaced apart while theliner is in the mould so that after extraction from the mould thecylinder of material can be slit while the liner is still in place. Theouter edges of these flanges have lips 173 bent back parallel to theliner surface and forming a recess therewith. These recesses areengageable by the inwardly directed jaws ofa locking clip 175, thecross-sectional form of which is shown in FIG. 2, and which isaccommodated in a suitably shaped longitudinal groove 176 in the mouldsurface. The clip 175 thus co-operates with the edge pieces 171 to holdthe edge portions of the liner together when the cylinder and liner areremoved together from the mould, as will be described, thus holding thecement cylinders on the mandrel when removed from the mould. Tofacilitate removal from the mould, the outside surface of the liner, andthe inside surface of the mould, are coated withpolytetrafluoroethylene.

The mandrel 140 used with this mould is an expanding mandrel as shown inFIGS. 3 and 4. The mandrel includes a cylindrically curved surfaceformed by a slightly flexible metal plate 141, the longitudinal edges ofwhich are close together when the plate 141 is unstressed and is at itsminimum diameter as indicated in full lines in FIG. 4. The plate 141 hasan annular end flange 142 at one end, and is capable of being expandedby means to be described to the condition shown in broken lines in FIG.4, the amount of radial expansion being greater than the radial depth offlange 142.

The mandrel is mounted on a tubular shaft 144 carried at its inner endby a rail mounted carriage 148, the carriage allowing axial movement ofthe mandrel into the mould and also allowing free rotation of the shaft144. The shaft 144 has an extension 145 at the outer end of the mandrel(i.e., that remote from the carriage 148), which serves a purpose to bedescribed. The shaft 144 carries two axially spaced expandingarrangements 151 and 152 by which the plate 141 is connected to theshaft 144. Each expanding arrangement comprises two opposed pairs ofgussets 154 welded to shaft 144 and two symmetrically arrangedtriangular crank members 155 each having a first corner pivoted at 156to gussets 154, a second corner pivoted to gussets 157 which are weldedinternally to plate 141 near to the longitudinal edges thereof, and athird corner pivotally connected by links 158 to gussets 159. Both crankmembers 1.55

and links 158 are of channel form, having parallel side members areconnected for movement together by plate 155a. The gussets 159 arewelded to the inside of plate 141 at locations spaced away from gussets157, being on the opposite side of a plane through pivots 156 from thesegussets 157. The spacing between adjacent gussets 157 and 159 is roughlyequivalent to that between the two gussets 159, this spacing being ofthe order of to of arc subtended at the axis of shaft 144. The two crankmembers are arranged to be urged apart by a pneumatic cylinder 161, thiscylinder being connected by a flexible conduit 162 via a rotary shut offvalve 163 to an air space within the hollow shaft 144. The space withinthe shaft 144 is closed apart from the conduit 162 and a quick connectorcoupling by means of which a charge of compressed gas can be admittedinto this space. The valve 163 is biassed into a shut position, but isarranged to be opened by rotary movement which occurs when the valve arm163a, extending radially from the inside end of the mandrel, is pivotedsideways by contact with an arm 164 which rotates with the mould.Admission of pressurized air into cylinder 161 is arranged to causeextension of this cylinder, with consequent outwards movement of members155 and expansion of the plate 141 into the broken line position. Thepivotal movement of valve arm 163a is limited so that after the valve163 has been opened by arm 164 of the mould these arms continue toengage with each other causing rotation of the mandrel with the mould.The arms 163a and 164 are so situated on the mandrel and mouldrespectively as to cause the mandrel to be rotated with the mould insuch position that the adjacent longitudinal edges of the plate 141forming the mandrel surface are disposed adjacent the junction in theliner (see FIG. 2), so that after expansion of the mandrel a gap isprovided in the cylindrical surface of the mandrel which gap underliesthat between the flanges 172 of the liner.

The outer end of the mandrel is provided with a protruding spring loadedplunger 166, positioned to engage the void ring 121 so that this voidring is pushed away from a cement cylinder formed in the mould onpositioning of the mandrel in this cylinder.

In operation, liner 170 is fitted into the mould, the end plate 122 isplaced in the closed position, and the void ring 121 placed in the innerposition shown in FIG. 1. With the shutter 38 of the charging head 23held closed by cylinder 81, the trough formed by this shutter is filledwith aggregate material. The charging head 23 is then advanced into themould on rails 24a, to the position of FIG. 1. The cylinder 84 isactuated to bring the spreader means 86 close to the mould surface, andcylinder 81 is operated to open the shutter 38 to the position shown infull lines, thus dumping the aggregate material which distributes itselfwithin the mould. A cement mix is then fed onto the mould surface viathe pipes 36 and 36a, and simultaneously the cylinder 84 is operated toraise the spreader means 86 gradually, so that these maintain contactwith the cement mix and ensure that this is spread evenly within themould. The cement mix is fed in while wet (with about 70 percent water)and rotation of the cylinder at a peripheral speed of 1,200 ft/min forabout five minutes causes the wet cement to form a cylindrical layer 149of uniform wall thickness on the inside of the mould, within an outerlayer of aggregate. The void ring 121 defines the end of the cylinder149 of cement remote from plate 122. The centrifugal effect alsoconcentrates and compacts the solid particles of the mix in the outerparts of the cement layer, and excess water is forced to the center ofthe mould and flows out of this during a de-watering stage.

The use of a cement mix containing only 70 percent water is in contrastto other methods where more than 90 percent excess water is required.

The de-watering stage is reached after the material has spunsufficiently to compact the solids into cylindrical form and to form aninner-layer of excess water. This takes about one minute. At this stagethe cylinder 89 is operated to cause skimmer 88 to protrude from thelower surface of the spreader means, and cylinder 84 is operated to movethe member 83 downwardly until the skimmer contacts the layer of waterwithin the mould. The water is then skimmed off by pumping this throughdischarge pipe 90. In the final stages of dewatering, the spreader means86 is brought into contact with the cement cylinder, and the vibrator 92is activated to cause vibration of the spreader means, and compaction ofthe cement, while the mould continues to spin.

Once a hollow cement cylinder has been formed, and the de-watering andcompacting steps have also been performed as described for the firstembodiment, the end plate 122 is lifted clear (as in FIG. the spacewithin the shaft 144 is charged with compressed air, and the mandrel 140is inserted into the cylinder, while the cylindrical mandrel surfaceformed by plate 141 is in its relaxed, contracted state, and while themould is still spinning, so that the cement cylinder is maintained incontact with the liner.

As the mandrel approaches the position shown in FIG. 5, the plunger 166pushes the void ring 121 away from the end of the cement cylinder 170,to the position shown in FIG. 5. In the latter stages of this movement,the flange 142 passes beyond the end of the cement, allowing expansionof the mandrel to occur. In this latter'stage also, the valve arm 163aof the nonrotating mandrel strikes the arm 164 of the rotating mould,causing, firstly, rotation of the mandrel with the mould, and secondlyopening the valve 163 to allow pressurized air to pass via co nduits 162from the interior of shaft 144 to air cylinder 16]. Air cylinder 161then expands, causing expansion of the outer surface of the mandrel intocontact with the interior of the cement cylinder 149, with consequentexpansion of the flange 142 into the space between the end of the cementcylinder and the void ring 121. Rotation of the mould is then stopped,the parts being then positioned as shown in FIG. 5. The carriage 148 isthen withdrawn, carrying the mandrel which in turn causes the cementcylinder 149 together with liner 170 to be slid (without dimensionalchange) from the mould. During this movement, flange 142 acts asextractingmeans engaging the outer end of the cement cylinder andpreventing the cement cylinder and liner from sliding off the mandrel.

FIGS. 6a and 6b show means for slitting the cylinders and laying out theresultant sheets. As shown, a series of similar pallets 185 is provided,each having a lug 186 extending along one edge and adapted to engage inthe recesses of edge pieces 17] of the liners. As shown in FIG. 6b, justoutside the lug 186 and parallel thereto is situated one strand 187 of awire band saw, which saw is vertically movable relative to the pallet.

At each side of the pallets 185 is situated a vertical wall 189, havinga horizontal tapered upper edge suitably spaced to engage an annularrecess in the support shafts 144, of the appropriate end of mandrel 140,as shown in FIG. 6a. The walls 189 are adjustable in height by raisingmeans indicated at 190. When raised to their full height, the walls 189are capable of forming a steam curing chamber when combined with theparts shown in FIG. 6c. These parts comprise a top 191 suitable forcovering the space between walls 189, and hinged end pieces 192 sized toclose the ends of the chamber.

In operation of the apparatus shown in FIG. 6, a first pallet 185 islaid between the walls 189 while the walls are in a lowered position.After a cement cylinder has been removed from the mould on the mandrel140, the mandrel is positioned directly above the band saw 187, with itssupport shafts 144, 145 supported at one end of walls 189, and with theliner edge portions positioned as shown in FIG. 6b. The clip is removedfrom the liner, and one edge portion only of the liner is thenre-attached to the mandrel by two U-clips shown at 194, which haveopposed flanges engaging the inside of the mandrel and the outside ofthe edge piece 171, one clip being used at each end of the mandrel. Theother edge portion 171 is engaged by lug 186 as shown in FIG. 6b. Thewire band saw 187 is then operated to cut through the cement cylinder,the saw passing between the liner edge portions, by deflecting the edgeportions where they abut. The cylinder and liner are then rolled outflat on the pallet 185, with one end of the liner remaining attached tothe pallet and the other end remaining clipped to the mandrel untilenrolled. During this unrolling operation, the mandrel support shaft 144and 145 roll and slide along the top edges of walls 189, the movement ofthe mandrel being such as to stretch and roll the sheet of cement.

After a first sheet of cement has been laid out as described, a furtherpallet a is laid thereon, and the next sheet is laid on this furtherpallet, this operation being repeated until a stack of palletsinterposed with sheets of cement and liners is produced. As successivesheets of cement and pallets are laid down, the walls 189 are raised byraising means 190, so as to continue to support the mandrel during eachunrolling operation. After a stack of about 20 cement sheets have beenlaid out in this manner, and with the walls 189 raised to their maximumheight, a curing chamber is formed by arranging on these walls the top191 and end pieces 192 as shown in FIG. 60. The stack of cement sheetsis then steam cured to harden them after which the sheets are removedand the pallets and liners recovered for re-use. It may be noted thatthe sheets are cured and hardened without being moved from the positionin which they are laid out.

The liners may be re-used by being bent up around a suitable mandrel,and cleaned on their external surfaces before being inserted into themould. After insertion into the mould the inner surfaces are cleaned andoiled while the mould is slowly rotated.

The mandrel described may of course be modified in various respects.Thus it is not essential that the air reservoir be provided by the spacewithin the shaft 144; instead a separate reservoir, rotatable with themandrel, could be used. Also, the valve actuator need not be pivotal,the essential feature being that this extends outwardly beyond thecylindrical surface of plate 141; and may be moved to open the valve bymeans on the mould which engages the valve actuator when the mandrel isalmost fully inserted into the mould. Furthermore, a compressed gasother than air may be used.

The apparatus shown in FIGS. 7 to 14 includes a modified mouldparticularly shown in FIGS. 7 and 8. This mould is generally similar tothat of the previous embodiment in having a rotatable cylindrical shell212 held by reinforcing rings 215, which rest on rollers 216 rotated bymeans similar to those described in the previous embodiment. The mouldhas a fixed end plate 221 held by studs 221b, and a removable end plate222 mounted by means similar to. those described with reference to FIGS.1 and 2 and which will not be further described. The fixed end plate 221is of annular form, having a central aperture large enough to admit acharging head 223, similar to charging head 23 already described.

The mould as shown in FIG. 7 also includes a removable liner 240, in theform of a sheet of flexible metal having inwardly turned flanges 242along its opposite edges. When the liner is bent into cylindricalformand placed in a mould these flanges are spaced a short distanceapart and form opposite sides of a longitudinal division in a cementcylinder spun in the mould. Each flange 242 has a lateral extension 243,the extensions 243 overlapping and holding between them a strip ofsealing material 244 (see FIG. 8).

The flanges 242 each have two rows of apertures 246, namely an upper rowof apertures 246a and a lower row of apertures 246b. The upper apertures246a are adapted to be engaged by the mandrel in a manner to bedescribed with reference to FIG. 10. The lower apertures 246b of eachflange are engaged, as shown in FIGS. 7 and 8, by locking meansconstituted by a series of hooks 247 mounted on a shaft 248 extendinglongitudinally of the mould and carried by brackets 249 mountedexternally of the mould. The hooks 247 extend through apertures in themould wall to engage the liner apertures 246b, the space within themould occupied by these hooks being protected from ingress of cement bythe seal formed by sealing strip 244 and the flange extensions 243.Clearly, all the hooks of one series, i.e., attached to one of theshafts 248, can simultaneously be engaged with the apertures 24612 ofone flange, simply by rotating the respective shaft 248 by means of ahandle shown at 248a. The liner can thus be inserted into the mould withthe end plate 222 removed and with the hooks 247 in a position to clearthe flanges 242, and handles 248a are operated after insertion of theliner to hold this in position.

The apparatus also includes a special cylindrical mandrel 250, which isshown in FIG. 9. The mandrel has a cylindrical outer wall 250a, thediameter of which is selected so that this can be inserted into a cementcylinder which has been formed in the mould, to engage the inner surfaceof such a cylinder directly, without dimensional change of the cylinder.The ends of the mandrel are closed by end plates 251, to the centre ofwhich are welded tubular guide members in the form of shafts 252. a

One longitudinal portion of the mandrel, shown at 254 at the bottom ofFIG. 9 and enlarged in FIG. 10, is recessed, and this recessed portionis provided with holding means in the form of hooks 255 for engaging theupper apertures 246a of the flanges 242 of the liner. The hooks 255 arecarried by two parallel shafts 256, extending longitudinally of themandrel and supported by transverse members 257 within the recess 254 ofthe mandrel. As shown in FIG. 10, in one rotational position of eachshaft 256 the hooks 255 of that shaft engage with the apertures 246a ofone flange 242, and the shafts 256 are rotatable from this position to aposition in which the hooks 255 are clear ofthe flanges. Clearly, thehooks attached to one of the shafts can be engaged simultaneously withthe apertures 246a of one flange by rotation of the respective shaft 256by a handle 256a which extends out of the front of the mandrel; sinceshafts 256 are independently operable each edge of the liner can beselectively attached to the mandrel.

FIGS. 11 and 12 show end views of the mould in which a cement cylinder258 has been spun, and subsequently the mandrel 250 has been insertedinto the spun cement cylinder. As shown in FIG. 11 the hooks 247 of themould are still engaged with the flanges 242 of the liner, as in thespinning position, and hooks 255 of the mandrel are as yet not engagedwith the liner. As shown in FIG. 12, the hooks 247 of the mould havebeen disengaged by rotation of shafts 248, and the mandrel hooks 255have been engaged with the liner by the rotation of shafts 256. In thisposition, the liner is held securely by the mandrel, so that the mandrelcan be withdrawn from the mould with the liner holding the cementcylinder in place around the mandrel. It will be understood that theapparatus includes mounting means for the mandrel which may be in theform of ordinary handling means such as a hoist or small crane, andwhich supports the mandrel by the shafts 252. This mounting means mustallow axial movement of the mandrel into the mould, and rotation of themandrel after removal of the mandrel from the mould to allow the cementsheet to be unrolledl from the mandrel, while relative transversemovement is provided between the mandrel and the surface which receivesthe sheet. The mandrel may also be carried by the special handling means148 already described.

A further part of the apparatus is a surface onto which the cement sheetcan be laid after removal from the mandrel. A suitable pallet isindicated at 260 in FIGS. 13 and 14, the latter drawing showing anenlarged view of one end of the pallet. The pallet is a flat supportingsurface having lugs 262 projecting from one end, which lugs support arotatable shaft 265 extending along one edge of the pallet. The shaft265 carries hooks 264 which are engageable with the apertures 246b ofthe flanges 242 of the liner. A handle (not shown) is provided forrotating shaft 265, so that when the mandrel, with liner and cementcylinder in place, is to be laid out onto the pallet, one flange of theliner is firstly attached by the hooks 264 to the pallet andsimultaneously released by the corresponding mandrel hooks 255, thecement sheet being then unrolled as shown in FIG. 13, after which theother end of the liner is released from the mandrel.

In the first stage of the process using the apparatus of FIGS. 7 to 14 asuitable liner 240 is bent into cylindrical form and inserted into theend of the mould from which end plate 222 has been removed. The linerflanges 242 are suitably positioned within the mould and the liner isthen secured in position by rotating the handles 248a to engage hooks247 with the apertures

1. Apparatus for forming into sheet form a flowable hardenable materialsuch as a cement mix, comprising: a. a cylindrical mould mounted forrotation on a horizontal axis and having a removable end plate, saidmould and end plate being such that a cylindrical body formed within themould can be extracted by sliding without dimensional change afterremoval of said end plate; b. means for feeding said material directlyonto the inner surface of a liner held within said mould; c. a mandrelmovable axially into the mould through the end of the mould having theremovable end plate, said mandrel having a cylindrical surfaceengageable with the inside surface of a hollow cylindrical body of thematerial formed within the mould by spinning; d. mounting means for saidmandrel allowing movement thereof axially into the mould and alsoallowing rotation thereof after removal from the mould and allowingrelative transverse movement between the mandrel and a receiving surfacefor the sheet; e. a flexible liner dimensioned to fit within thecylindrical inner surface of the mold, the edges of said liner which areadjacent each other when in the mould being provided with radiallyextending elements; f. releasable connecting means for holding saidradially extending elements to prevent separation thereof after removalof said mandreal, with said hollow cylindrical body and said liner, fromthe mould, and g. means for forming a longitudinal division in saidcement body, to allow the body to be unrolled from the mandrel afterremoval from the mould.
 2. Apparatus according to claim 1, wherein saidradially extending elements are inwardly directed flanges which are ofgreater radial extent than the radial difference in dimensions betweenthe curved outer surface of the mandrel and the curved inner surface ofthe mould, whereby said flanges also constitute said means for forming alongitudinal division in said cement body.
 3. Apparatus according toclaim 1, wherein said radially extending elements are outwardly directedflanges which flanges are spaced apart while the liner is in the mouldso that after extraction from the mould the cylinder of material can beslit while the liner is still in place.
 4. Apparatus according to claim3, further including clip means adapted to engage said outwardlydirected flanges of the liner when the cylinder is being removed fromthe mould, said clip means being removable to allow slitting means forforming the longitudinal division in said cement body to pass betweenthe liner edges.
 5. Apparatus according to claim 1, wherein said mouldincludes an annular member situated in said mould so as to define an endof said cylinder remote from that end adjacent the removable end plate,said annular member being movable axially of the mould and away from theend of said cylinder formed therein, and wherein said means for holdingthe cylinder on the mandrel includes extracting means contractible tothe internal diameter of a cylinder formed within the mould andexpandible into a space formed between said annular member and thecylinder on movement of said member away from the formed cylinder,whereby the said extracting means can engage the end of the cylinderremote from the removable end plate to hold the cylinder on the mandrelwhile the mandrel is withdrawn from the mould.
 6. Apparatus according toclaim 2, wherein said releasable connecting means includes hook membersmovably mounted on said mandrel and engageable with said inwardlydirected flanges.
 7. Apparatus according to claim 6, wherein saidmandrel includes hook members engageable selectively with one or otheror both of the flanges of said liner, whereby both edges of the linerare individually attachable to the mandrel.
 8. Apparatus according toclaim 7, wherein said liner flanges are provided with elementsengageable by locking means carried by the mould.
 9. Apparatus accordingto claim 8, wherein said liner edges include flanges having apertures,and wherein said apertures of each flange are engageable by a series ofhooks carried on a shaft rotatably mounted on the mould, said hooks ofeach series being simultaneously engageable with said apertures of oneflange by rotation of the respective shaft.
 10. Apparatus for forminginto sheet form a flowable hardenable material such as a cement mix,comprising: a. a cylindrical mould mounted for rotation on a horizontalaxis and having a removable end plate, said mould and end plate beingsuch that a cylindrical body formed within the mould can be extracted bysliding without dimensional change after removal of said end plate; b.means for feeding said material directly onto the inner surface of aliner held within said mould; c. a mandrel movable axially into themould through the end of the mould having the removable end plate, saidmandrel having a cylindrical surface engageable with the inside surfaceof a hollow cylindrical body of the material formed within the mould byspinning; d. mounting means for said mandrel allowing movement thereofaxially into the mould and also allowing rotation thereof after removalfrom the mould and allowing relative transverse movement between themandrel and a receiving surface for the sheet; and e. a flexible linerdimensioned to fit within the cylindrical inner surface of the mould,the edges of said liner which are adjacent each other when in the mouldbeing provided with radially extending flanges, said flanges extendinginwardly by an amount greater than the radial difference in dimensionsbetween the curved outer surface of the mandrel and the curved innersurface of the mould, whereby said flanges constitute means for forminga longitudinal division in said cement body, to allow the body to beunrolled from the mandrel after removal from the mould;
 11. Apparatusaccording to claim 1, wherein said cylindrical surface of the mandrel isconstituted by a cylindrically curved, flexible plate, and wherein saidmandrel includes means for expanding said plate after insertion of themandrel into a cylinder in the mould.
 12. Apparatus according to claim11, wherein said plate includes an outwardly directed flange at theouter end of the mandrel, said expanding means being capable of causingradial expansion of said plate by an amount at least equivalent to theradial extent of said flange, whereby said flange can be caused toengage the end of a cylinder of material formed in the mould to assistin sliding the cylinder from the mould.
 13. A mandrel for use inremoving a hollow cylinder of material centrifugally formed within amould, comprising:-a cylindrically curved, flexible plate. a shaftextending axially of said plate and being mounted for continuousrotation in a support, expanding means including a linkage connectingsaid shaft with said plate, and also including a pneumatic cylinderconnected to said linkage in such manner as to cause said linkage toexpand said plate when the cylinder is supplied with pressurized gas, agas reservoir contained within the mandrel and rotatable therewith,connector means being provided so that said reservoir can be pressurizedwith compressed gas at least when the mandrel is stationary, conduitmeans connecting said reservoir to said pneumatic cylinder, shut-offvalve means interposed in said conduit means, and a valve actuator foroperating said valve means, whereby said reservoir can be charged withcompressed gas via said connector means while the mandrel is stationary,and whereby said valve actuator may be operated upon insertion of themandrel into a mould to cause compressed gas in said reservoir tooperate said expansion means while the mandrel is rotating.
 14. Amandrel according to claim 13, wherein said plate includes an outwardlydirected flange at the outer end of the mandrel, said expanding meansbeing capable of causing radial expansion of said plate by an amount atleast equivalent to the radial extent of said flange, whereby saidflange can be caused to engage the end of a cylinder of material formedin the mould to assist in sliding the cylinder from the mould.
 15. Amandrel according to claim 13, wherein said reservoir is a hollow spacewithin said shaft.
 16. A mandrel according to claim 13, wherein saidvalve actuator extends outwardly beyond the cylindrical surface of saidplate, whereby said valve actuator may be operated to open the valvemeans by a means on said mould which engages said valve actuator whenthe mandrel is almost fully inserted into the mould.